It's August, prime beach time. Almost four decades ago, "Jaws" made people think twice about their vacation plans to head to surf and sand. But times change. Consider "Blackfish," a documentary by Gabriela Cowperthwaite in theaters now that depicts the lives of killer whales in captivity and the trainers who interact with them.

The movie opens with a dark screen and the sounds of a 911 call being played back. "A whale ate one the trainers?" the dispatcher says in response to the Feb. 24, 2010, call about the death of SeaWorld trainer Dawn Brancheau in Orlando, Fla. Brancheau was killed by Tilikum, a bull orca whale at SeaWorld.

Brancheau's death caught the eye of Cowperthwaite, who, in addition to be a documentary filmmaker, is a mother who took her kids to SeaWorld. "It didn't square with any pop knowledge I had of SeaWorld," she said in an interview.

As Cowperthwaite got involved with making the movie that would become "Blackfish," the story continued to evolve. The focus on the trainers and work-safety issues at SeaWorld began to shift toward the conditions the whales were in — specifically, what could lead a killer whale to, well, kill a person.

"I backed into the entire whale issue. I'm not an animal activist. That's not my background," she said. But she found that she couldn't tell the story of the trainers without telling the story of the whales. "I saw them both as expendable commodities, victims of a larger system ... victims of the SeaWorld system, to be blunt," she said. The result is a movie that is sad, moving, terrifying — that tells a story that continues to reverberate.

After Brancheau was killed, the Occupational Safety and Health Administration recommended new guidelines for how trainers could interact with killer whales during training and public performances at water parks. SeaWorld challenged the regulations, and has turned to Eugene Scalia, a labor lawyer at Gibson Dunn and the son of Supreme Court Justice Antonin Scalia, to fight it out in court on its behalf.

What happens next might be affected by the public reaction to "Blackfish." How many people have gone to SeaWorld, or taken their kids to SeaWorld like Cowperthwaite, without thinking about the issues her film broaches? Can you view Shamu the same way after seeing what he's capable of and what kind of conditions and history led to that? How many people went to the beach without thinking about sharks before Steven Spielberg changed all that in 1975?

"I'm comfortable with the future as a question mark," Cowperthwaite said, knowing that her film ends with many uncomfortable unanswered questions about what's next in SeaWorld's battle with OSHA, or whether public perceptions about orcas will change. The relationship man has with whales is, to put it lightly, complicated. Anyone who's read "Moby Dick" can attest to that.

According to the filmmaker, that level of uncertainty is what makes making movies worthwhile. "I'm comfortable with filmmaking chaos ... I like not having an endpoint in sight and finding that in the filmmaking process. It grounds me to the audience," she said.

"Blackfish" is a movie on very solid ground. It's an exploration, ultimately, about man's relationship to wild animals, in this case killer whales. Where that exploration takes the audience is a journey that might not always be pleasant, but it's one worth taking.